Mineral lubricating oil containing polysulfides of thiophosphorous and thiophosphoric acid esters



Patented Oct. 17, 1950 MINERAL LUBRICATIN POLYSULFIDES OF ANDTHIOPHOSPHORIC ACID ESTERS Louis A. Mikeska, Westfield, N. J., assignorto Standard Oil Development Company, a corporation of Delaware G OILCONTAINING THIOPHO SPHOROUS No Drawing. Original application September19,

1946, Serial No. 697,919. Divided and this application October 1, 1948,Serial No. 52,419

7 Claims. (01. 252-461)) This invention relates to a mineral lubricatingoil and more particularly to a new type of additive which imparts pourstabilizing properties to such oil and improves other properties of thesame.

This application is a division of application Serial No. 697,919, filedSeptember 19, 1946, now issued as Patent No. 2,471,115, which is in turna continuation-in-part of application Serial No. 653,152, filed March 8,1946, now issued as Patent No. 2,443,264, granted June 15, 1948, whichis a division of application Serial No. 523,091, filed February 19,1944, now abandoned.

In accordance with the present invention a new class of organiccompositions are described which are useful as additives for minerallubricating oils, particularly those which are used in internalcombustion engines, in which they act as pour depressing and pourstabilizing agents, also as inhibitors of oxidation. 4

The new class of additives have been found not only to be effective insubstantially reducing the ASTM pour point of a lubricating oil, but instabilizing the pour point, thus providing a stable lubricating oilwhich will not solidify under conditions of fluctuating temperatureinvolved in normal outdoor conditions. The new additives of the presentinvention have been submitted to tests which simulate the normal varyingtemperature conditions encountered in winter field service, andsatisfactory results were obtained from their use, as will be explainedmore particularly hereinafter.

In serving as inhibitors of oil deterioration, the new additives aid inthe prevention of ring sticking, piston skirt varnish formation,deposition of sludge, and the like. They are particularly useful ininhibiting the normal corrosiveness of the oil when in contact withcopper-lead, cadmiumsilver and other similar bearings, now widely usedin automotive engines,

The'new class of compounds which are employed as additives in accordancewith the present invention are organic compounds containing bothphosphorus and sulfur and may beconsidered as polysulfide derivatives ofthiophosphoric and thiophosphorous acids, the latter being obtained byreacting a sulfide of phosphorus with a mixture of a wax-phenol and analiphatic alcohol. It has been found that the reaction product derivedfrom a mixture of a wax-phenol and an alcohol is superior to similarproducts derived from wax-phenol or other alkylated phenols aloneinpossessing superior oil solubility. It is believed that the presence ofthe alcohol prevents the formation of products of too high molecularweight.

When the mixture of wax-phenol and alcohol is reacted with phosphoruspentasulfide, it is believed that the reaction proceeds according to thefollowing equation:

In the above equation R represents the, waxphenol radical and/or, thealiphatic radical from the alcohol, the equation representing astatistical average of reactions among the various molecules.Undoubtedly in many cases the thiophosphoric acid molecule will containboththe waxphenol and the aliphatic radicals. In forming thepoly'sulfide derivatives of such thiophosphoric acid or thiophosphorousacid, the acid is treated with an oxidizing'agent, e. g., iodine,potassium triiodide, ferric chloride, sodium hypochlorite, or oxygenitself, or with sulfur dichloride or sulfur monochloride, to form adisulfide, trisulfide or tetrasulfide, respectively, according to thefollowing equations: 4(RO)2PSH 02 2 R0)lP-s-s 1 0R)l +2Hz0 2(RO)1PSHsol, (R0)zP-SS-S-P(OR)2 21101 2(RO 2PSH s,o12-- aonr-s-fi-s-monn 21101The wax-phenols employed in accordance with the present invention may bederived in the usual manner by first chlorinating paraffin wax and thenreacting the latter with phenol. The aliphatic alcohols which areemployed in conjunction with such phenols may be any aliphatic alcohols,particularly suitable examples being methyl alcohol, ethyl alcohol,isopropyl alcohol, octyl alcohol, decyl alcohol, stearyl alcohol, oleylalcohol,

and the like. The mixture of wax-phenol and alcohol may be reacted withany of the sulfides of phosphorus, such as P283, P285, P483, P467, andthe like.

The ratio of alcohol to phenol may be varied within wide limits. Thehigher the molecular weight of the wax phenol, the higher the ratio hasto be in order to obtain satisfactor oil solubility. Generally, apreferred ratio is one to two waxphenol hydroXyl groups to one moleculeof alco hol.

In employing the additives of the present invention for use either aspour depressants or as corrosion inhibitors it has been founddesirable-to use the same in the proportions of about 0.02% to 3%,preferably about 0.1% to 2%, based on the lubricating oil base stock.

In the following examples are present invention, and tests of the sameillustratillustrated methods for the preparation of typical products ofthe ing their usefulness when compounded with mineral lubricating oils.It is to be understood that these examples are illustrative only and arenot to be considered as limiting the scope of the invention in any way.

Example 1.-Preparation of substituted thiophosphoric acid A three-wayflask equipped with a stirrer and return condenser was charged with 51g. of waxphenol (prepared by heating 450 g. of chloroparai'lincontaining 14% 01 with 90 g. phenol in the presence of AIC13), 15.8 g.decanol (decyl alcohol), 22.2 g. Pass, and 150 cc. dioxane. (The amountsof wax-phenol and decanol were calculated to provide 2 wax-phenolhydroxyl groups for each molecule of decanol.) The mixture was refluxeduntil no more H28 was given of? (about 2 /2 hours). The reaction productwas then dissolved in ether and transferred into a large beakercontaining a volume ofwater approximately equal to the volume of theether solution. Then while the mixture was rapidly stirred, a slightexcess of hydrated lime was added. The mixture was stirred until theaqueous solution remained permanently alkaline to litmus. The etherlayer was then separated from the aqueous layer and the extract wasdried over calcium chloride. The ether was removed on a steam bath andthe residue was taken up with acetone. The small amount of undissolvedmaterial was filtered oif and the acetone was removed at 100 C. under 2mm. pressure. The product was obtained as a soft resin readily solublein lubricating oils.

Example 2.Preparation of the disulfide derivatire sulfate. On removal ofthe ether, a viscous reddish brown residue was obtained which was foundto be readily soluble in lubricating oils.

Example 3.-Preparation of the trz'sulfide derivatz'oe A portion of thesubstituted thiophosphoric acid obtained in the preparation of Example 1was dissolved in an equal volume Of dioxane and was treated with SClz inthe ratio of one mol of SC12 to 2 mols of the acid. The mixture was thenheated at 80 C. for about 2 hours, whereupon it was poured into waterand extracted with ether. The ether extract was then dried over sodiumsulfate. On removal of the ether the reaction product was obtained as aviscous brown oil, readily soluble in mineral oils.

Example 4Pour point and pour stability tests of Examples 2 and 3 in awaxy base mineral lubricating oil consisting of an acid-treatedMid-Continent neutral oil with the addition of ti Of Pennsylvania brightstock, this oil having a viscosity of SAE grade and a cloud point of +34F.

The pour stability of the various oil blends containing the newadditives was determined by a test in which the temperature was variedto simulate rather severe winter temperature conditions. Morespecifically, the samples were first gradually reduced in temperaturefrom room temperature to F. during the first day of the test, thenwarmed gradually to 45-50 F. during the second day, then held at about35 F. for two days, these temperatures being close to the cloud pointsof the oil samples, and finall the temperature was gradually lowered toto F. during the last 24 hours. The temperature at which the oil samplesbecame solid under these conditions was taken as the solid point. Theresults obtained with the tests applied to the unblended base oil and tothe same when blended with various concentrations of the originalwax-phenols and with the products of Examples 2 and 3 are shown in thefollowing table:

Additive Concentration Pour Stability (Solid Point), F..

ASTM Pour Oil Blend Point, O

Base Oil Base Oil-l-Wax-phenoL.

Base Oil-l-Product of Base Oil+Product of Example 5.Bearz'ng corrosiontest A test was made of the effect of the disulfide product of Example 2in reducing the corrosiveness of a lubricating oil toward a copper-leadbearing, using a blend containing 1% of the additive in a solventextracted Mid-Continent parafiinic lubricating oil of SAE viscositygrade. A similar test was made of the unblended base. The test wasconducted as follows: 500 cc. of the oil was placed in a glass oxidationtube (13 inches long and 2 inches in diameter) fitted at the bottom witha 4 inch air inlet tube perforated to facilitate air distribution. Theoxidation tube was then immersed in a heating bath so that the oiltemperature was maintained at 325 F. during the test. Two quartersections of automotive bearings of copper-lead alloy of known weighthaving a total area of 25 sq. cm. were attached to opposite sides of astainless steel rod which was then immersed in the test oil and rotatedat 600 R. P. M., thus providing suificient agitation of the sampleduring the test. Air was then blown through the oil at the rate of 2 cu.ft. per hour. At the end of each 4-hour period the bearings wereremoved, washed. with naphtha and weighed to determine the amount ofloss by corrosion. The bearings were then repolished. (to increase theseverity of the test), reweighed, and then subjected to the test foradditional 4- hour periods in like manner. The results are given in thefollowing table as corrosion life,-

Bearing Cor- Oil rosion Life,

Hours Base Oil Q. 4 Base Oil +1% Product of Ex. 2 20 The products of thepresent invention may be employed not only in ordinary hydrocarbonlubricating oils but also in the heavy duty type of lubricating oilswhich have been compounded with such detergent type additive as metalsoaps, metal petroleum sulfonates, metal phenates, metal alcoholates,metal alkyl phenol sulfides, metal organo phosphates, thiophosphates,phos- -phites and thiophosphites, metal salicylates,

metal xanthates and thioxanthates, metal thiocarbamates, amines andamine derivatives, reaction products of metal phenates and sulfur,reaction products of metal phenates and phosphorus sulfides, metalphenol sulfonates, and the like. Thus, the polysulfide derivatives ofthe organo-substituted thio acids of phosphorus may be used inlubricating oils containing such addition agents as barium tert.-octylphenol sulfide, calcium tert.-amy1 phenol sulfide, nickel oleate, bariumoctadecylate, calcium phenyl stearate, zinc diisopropyl salicylate,aluminum naphthenate, calcium cetyl phosphate, barium di-tert.- amylphenol sulfide, calcium petroleum sulfonate, zinc methyl cyclohexylthiophosphate, calcium dichlorostearate, etc.

The lubricating oil base stocks used inthe compositions of thisinvention may be straight mineral lubricating oils or distillatesderived from paraffinic, naphthenic, asphaltic or mixed base crudes, or,if desired, various blended oils may be employed as well as residuals,particularly those from which asphaltic constituents have been carefullyremoved. The oils may be refined by conventional methods using acid,alkali and/or clay or other agents such as aluminum chloride, or theymay be extracted oils produced, for eX- ample, by solvent extractionwith Solvents of the The lubricating oils, however they may have beenproduced, may vary considerably in viscosity and other propertiesdepending upon the particular use for which they are desired, but theyusually range from about 40 to 150 seconds Saybolt viscosity at 210 F.For the lubricating of certain low and medium speed Diesel engines thegeneral practice has often been to use a lubricating oil base stockprepared from naphthenic or aromatic crudes and having a Sayboltviscosity at 210 F. of to 90 seconds and a viscosity index of 0 to 50.However, in certain typesof Diesel service, particularly with high speedDiesel engines, and in aviation engine and other gasoline engineservice, oils of higher viscosity index are often preferred, forexample, up to '75 to 100, or even higher, viscosity index. I

In addition to the materials to be addedaccording to the presentinvention, other agents may'also be used such as dyes, pour depressors,heat thickened fatty oils, sulfurized fatty oils, organo metalliccompounds, metallic or other soaps, sludge dispersers, antioxidants,thickeners, viscosity index improvers, oiliness agents, resins, rubber,olefin polymers, voltolized fats, voltolized mineral oils, and/ orvoltolizedwaxes and colloidal solids such as graphite or zinc oxide,etc. Solvents and assisting agents, such as esters, ketones, alcohols,aldehydes, halogenated or nitrated compounds, and the like may also beemployed.

Assisting agents which are particularly desirable are the higheralcohols having eight or more carbon atoms and preferably'12 to 20carbon atoms. The alcohols may besaturated straight and 1 branched chainaliphatic alcohols such as octyl alcohol (CcHrzOI-I), lauryl alcohol(CmI-IzsOl-I), cetyl alcohol (CrcHasOI-I), stearyl alcohol, sometimesreferred to as octadecyl alcohol (CISOS'lH), heptadecyl alcohol(CnHssO-H) and the like; the corresponding olefim'c alcohols such asoleyl alcohol; cyclic alcohols, such as naphthenic alcohols; and arylsubstituted alkyl type of phenol, sulfur dioxide, furfural,dichlorodiethyl ether, nitrobenzene, crotonaldehyde, etc.

Hydrogenated oils or white oils may be employed as Well as syntheticoils prepared,'for example, by the polymerization of olefins or by thereaction of oxides of carbon with hydrogen or by the hydrogenation ofcoal or its products. In certain instances cracking coil tar fractionsand coal tar or shale oil distillates may also be used. Also, forspecial application, animal, vegetable or fish oils or theirhydrogenated or voltolized products may be employed, either alone or inadmixture with mineral oils.

For the best results the base stock chosen should normally be that oilwhich Without the new additives present gives the optimum performance inthe service contemplated. However, since one advantage of the additivesis that their use also makes feasible the employment of lesssatisfactory mineral oils or other oils, no strict rule can be laid downfor the choice of the base stock. Certain essentials must of course beobserved. The oil must possess the viscosity and volatilitycharacteristics known to be required for the service contemplated. Theoil must be a satisfactory solvent for the additive, although in somecases auxiliary solvent agents may be used.

alcohols, for instance, phenyl octyl alcohol, or octadecyl benzylalcohol or mixtures of these various alcohols, which may be pure orsubstantially pure synthetic alcohols. One may also use mixed naturallyoccurring alcohols such as those found in wool fat (which is known tocontain a substantial percentage of alcohols having about 16 to 18carbon atoms) and in sperm oil (which contains a high percentage ofcetyl alcohol) and although it is preferable to isolate the alcoholsfrom those materials, for some purposes, the wool.

fat, sperm oil or other natural products rich in alcohols may be usedper se. Products prepared synthetically by chemical processes may alsobe used, such as alcohols prepared by the oxidation of petroleumhydrocarbons, e. g., para-11in wax, petrolatum, etc. p

In addition to being employed in crankcase lubricants the additives ofthe present invention may also be used in extreme pressure lubricants,engine flushing oils, industrial oils, general machinery oils,processoils, rust preventive compositions, and greases.

What is claimed is:

1. A mineral lubricating oil containing 0.02% to 3% of a compound of theformula where R and R each represents a member of the group consistingof wax-phenyl and aliphatic hydrocarbon radicals, and in any given'portion'of the compound represents substantial proportions of both suchradicals; and where n represents 0 or 1, and :1: represents an integerfrom 2 to 4.

2. A composition according to claim 1 in which n of the formularepresents 1.

3. A composition according to claim 1 in which n of the formularepresents 1 and ac represents 3. 4. A mineral lubricating oilcontaining 0.02% to 3% of a compound of the formula RO\IS| fi/OR P-s,-PRO/ OR where R and R each represents a member of the group consisting ofwax-phenyl and decyl radicals, and in any given portion of the compoundrepresents substantially equal numbers of REFERENCES CITED The followingreferences are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,343,831 Osborne Mar. 7, 19442,443,264 Mikeska June 15, 1948

1. A MINERAL LUBRICATING OIL CONTAINING 0.02% TO 3% OF A COMPOUND OF THEFORMULA